gpiolib: Free the last requested descriptor

The current code only frees N-1 gpios if an error occurs during
gpiod_set_transitory, gpiod_direction_output or gpiod_direction_input.
Leading to gpios that cannot be used by userspace nor other drivers.

Cc: Timur Tabi <timur@codeaurora.org>
Cc: stable@vger.kernel.org
Fixes: ab3dbcf7

 ("gpioib: do not free unrequested descriptors)
Reported-by: Jan Lorenzen <jl@newtec.dk>
Reported-by: Jim Paris <jim@jtan.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>